XRPD patterns

The analysis of XRPD patterns is an important tool studying the crystallographic structure and composition of powder compounds including the possibility to study deviation from ideal crystallinity, i.e. defects. Looking at an X-ray powder diffractogram the peak position reflects the crystallographic symmetry (unit cell size and shape) while the peak intensity is related to the unit cell composition (atomic positions). The shape of diffraction lines is related to defects , i.e. deviation from the ideal crystallinity finite crystallite size and strain lead to broadening of the XRPD lines so that the analysis of diffraction line shape may supply information about sample microstructure and defects distribution at the atomic level. 

A derived crystal packing model proved to be useful in resolving the crystal structure of a metastable polymorph of racemic modafinil, where details of the solved crystal structure of one polymorph was used as a basis for developing the structure of the other [12]. It was found that the calculated XRPD pattern matched well with the experimental data, indicating the correctness of the analysis. The powder diffraction of two polymorphs of chlorothalonil were solved to obtain... 

Fig. 10.11 The small-angle XRPD patterns ofthe precursors A, U and their hybrid material MA.u-...

Figure 1. XRPD patterns of Y-zeolites after 1 hour evacuation at 240 °C. The patterns were recorded at the evacuation temperature.

Figure 2. XRPD patterns of Na-Y, Cd-Y, and CdCl2/ NaY mixture. The patterns of Na-Y and Cd-Y were recorded at 220 °C after 1-hour evacuation at the same temperature. The pattern of the mixture was recorded right when the slowly raised evacuation temperature reached 220 °C (0 min), and after additional 4-hour evacuation at 220 °C (240 min).

Useful tabulations of the XRPD patterns of a number of compounds have been published by Koundourellis and coworkers, including 12 diuretics [31], 12 vasodilators [32], and 12 other commonly used drug substances [33]. These compilations contain listings of scattering angles, d-spacings, and relative intensities suitable for the development of acceptance criteria. 

Dorzolamide has been found to exist in two non-solvated polymorphic forms, which are distinguishable on the basis of their characteristic x-ray powder diffraction patterns. Typical XRPD patterns for Forms 1 and II are shown in Figures 1 and 2, respectively. Form I has been shown to be the more thermodynamically stable form at ambient temperature. 

Indinavir sulfate, produced as the ethanolate using the synthetic process described in Section 2, is crystalline as determined by the x-ray powder diffraction (XRPD) method. The XRPD pattern and associated data, obtained using a Phillips Model APD 3720 x-ray diffractometer, is shown in Figure 3 and Table 1 [7]. 

As shown in Figure 5, the XRPD pattern calculated from the crystal structure results was found to be very similar to the experimental XRPD obtained for the bulk product. The dissymmetry of all chiral centers... 

The X-ray powder diffraction (XRPD) pattern of a sample of atorvastatin calcium, Form-I, was recorded at room temperature on Bruker D8 Advance diffractometer (Karlsruhe, Germany), using nickel-filtered Cu Ka radiation. The sample was mounted in a polymethylmethacrylate sample holder, and analyzed in a continuous mode with a step size of 0.01° and a step time of 1 s over an angular range of 3-40° 26. The XRPD results are found in Fig. 1.18 and in Table 1.3, being evaluated with the DIFFRACplus EVA (version 9.0) diffraction software. 

TABLE 1.3 Scattering angles, interplanar c/-spacing, and relative intensities in the XRPD pattern of atorvastatin calcium, Form-1... 

FIGURE 1.19 XRPD pattern of atorvastatin calcium, Pfizer Form-1, scanned and digitized from the pattern disclosed in US patent 5,969,156. 

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